1. Field of the Invention
The present invention relates to a color filter, and more particularly, to a color filter using photonic crystal structures as the color filter layer thereof.
2. Description of Related Art
Because of its excellent display quality and economic advantage, cathode ray tubes (CRTs) have dominated the market in recent years. However, it may not be a perfect choice for a user who simultaneously operates several computer terminals/displays, or from the view of environmental protection. In view of the energy saving trend, the CRT has many problems, such as limited space utilization and considerable energy consumption. In particular, the CRT is not capable of providing a solution to meet the light, slim, short and small tendency today and the demand on low power consumption. Therefore, the thin film transistor liquid crystal display (TFT LCD) with the predominant features, such as high display quality, high space utilization, low power consumption and no radiation, gradually becomes the main stream of the market. market.
Currently, LCDs are in progress towards full colorization, large screen, high resolution and low cost, wherein the color display effect is achieved normally by utilizing a color filter. A color filter is usually disposed on a transparent glass substrate, where a black matrixes (BM) for light-shielding and color filter units respectively corresponding to each pixel in specific arrangement, for example, red filter units, green filter units and blue filter units, are disposed.
Recently, a sort of color filter adopting a photonic crystal structure as the color filter layer thereof has been developed. In 1987, Professors Eli Yablonovitch and Sajeev John together initially presented the photonic crystal principle. According to the principle, the light in some frequency bands is not able to exist in a photonic crystal structure by means of a periodic arrangement of different refractive indices. In other words, a photonic crystal itself does not possess a specific color, but allows a light with a specific wavelength to be transmitted based on a special design consideration, so as to emit red light, green light or blue light.
In US Patent Publication No. 20030218704 filed by Samsung Electronics Co., Ltd., a reflective display element is provided, wherein a photonic crystal structure serves as the color filter layer in an LCD panel and a light-filtering effect is achieved by using the optical forbidden area of a photonic crystal to reflect the light having a specific wavelength. For example, in order to get blue light, a photonic crystal structure is used to substitute the traditional blue photoresist and the hole dimensions and structure periodic intervals of the photonic crystal must be configured through design, so that the desired optical forbidden area is corresponding to the wavelength of blue light.
Since the structure periodic intervals and dimensions respectively corresponding to red light, green light and blue light are different from each other, three additional photolithography processes are required, which increases the fabrication complexity and reduces the production yield. Besides, an optical forbidden area possesses a specific frequency width, which would result in the problem of insufficient color saturation with the color filter layer by using a photonic crystal structure.